Energy production from algae in photo bioreactors enriched with carbon dioxide

ABSTRACT

A cyclic system composed of several integrated cyclic processes and a method for production of cement and or quicklime, ammonia, desalinated water and an excess of algae cells. The system comprises of: at least cement/quicklime production plant, at least ammonia production plant, at least one water desalination unit, at least one photo bioreactor. The energy source of the system is sunlight energy. The CO 2  produced by the system and other waste products are sequestrated and recycled for additional cycles of system operation. No CO 2  is released to the atmosphere. The system produces a huge excess of algae cells that accumulates in arithmetic or geometrical progression. The excess of algae cells can fuel additional energy consuming plants attached to the system or can be used for other various purposes such as food and food additives.

FIELD OF THE INVENTION

The present invention generally relates to the field of cement/quicklimeproduction, ammonia production, water desalination and electric powerproduction by sunlight energy mediated by algae cell.

BACKGROUND OF THE INVENTION

A presentation titled “Experimental study on sequestrating of CO₂ in thetrue flue gas by ammonia spray and producing NH₄HCO₃ by Zhang, Y., Li,Z.-Z., Li, C.-Z., Dong, J.-X. and Wang, Y. from the National Power PlantCombustion Engineering Research Center, Shenyang, China, is incorporatedherein by reference in its entirety.

U.S. Pat. No. 6,477,841, which is incorporated herein by reference inits entirety, discloses a closed cycle power plant for conversion ofsolar to electrical energy has water tank for growing macroalgae andfluidized bed combustion chamber for combusting macroalgae in presenceof oxygen and carbon dioxide.

EP0561436B1, which is incorporated herein by reference in its entirety,discloses a process for making cement by preheating the raw meal in acyclone heater, calcining the preheated raw meal, burning the calcinedraw meal in a rotary kiln, cooling the cement clinker formed in therotary kiln and grinding the cement klinker.

US20020194782, which is incorporated herein by reference in itsentirety, discloses an integrated biomass gasification and fuel cellsystem wherein the electrochemical reaction in the fuel cell is effectedby providing the reactant gases from a gasifier.

WO2000057105, which is incorporated herein by reference in its entirety,discloses a closed cycle power plant for the conversion of solar energystored by photosynthesis to electrical energy, comprising a body ofwater for growing macroalgae therein, and a fluidized bed combustionchamber for at least partial combustion of partially dried macroalgaehaving a water content of up to 60% wt/wt, the combustion being carriedout in an artificial atmosphere of oxygen and carbon dioxide.

WO1995024548, which is incorporated herein by reference in its entirety,discloses an internal combustion engine comprising combustion chambermeans, inlet track means, for directing air into the combustion chambermeans, and fuel induction means, for supplying powdered fuel to beburned in the combustion chamber means, in which the fuel inductionmeans are arranged for supplying the powdered fuel into the inlet trackmeans, so that the so supplied powdered fuel forms a substantiallyhomogenous fuel/air mixture for ignition in the combustion chambermeans, during the engine's operation.

U.S. Pat. No. 5,659,977, which is incorporated herein by reference inits entirety, discloses an integrated plant including a microalgaeproduction plant for growing, harvesting and drying algae and a fossilfuel-motor-generator plant producing electrical energy. A fossil fuelengine produces hot exhaust gas from which sensible heat dries thealgae. The drying may be direct from the exhaust gas or may be indirectwith the hot exhaust gas exchanging sensible heat with a recirculatingstream of inert gas. Carbon dioxide from the exhaust gas is recoveredfor use as a nutrient in the microalgae production plant. Electricalenergy from the generator is used to drive motors and/or produceartificial illumination and/or drive pumps, motors and controls in themicroalgae production plant.

U.S. Pat. No. 6,477,841, which is incorporated herein by reference inits entirety, discloses a method for the conversion of solar energystored by photosynthesis to electrical energy, utilizing a closed cyclepower plant comprising a body of water for growing macroalgae therein,and providing a fluidized bed combustion chamber for at least partialcombustion of partially dried macroalgae having a water content of up to60% wt/wt, the combustion being carried out in an artificial atmosphereof oxygen and carbon dioxide.

WO2007047805, which is incorporated herein by reference in its entirety,discloses a device and method for carbon dioxide sequestering involvingthe use of a photo-bioreactor with Light Emitting Diodes (LED's) for thecost-effective photo-fixation of carbon dioxide (CO₂). This device andmethod is useful for removing undesirable carbon dioxide from wastestreams.

BRIEF SUMMARY

The system comprises a basic core of three cyclic processes,synergistically integrated. These three cycles supply energy, rawmaterials and products to each other. To this basic core additionalcyclic processes can be added in such a way that they use the energy andthe products produced by the basic core to produce additional productsby these attached cycles. The basic core produces by sunlight energy:cement/quicklime, a huge excess of chemical energy (fuel), ammonia andin addition, by the same amount of sunlight energy—a huge amount ofdesalinated water. The system fully recycles its carbon source andnitrogen source, without emitting them outside the system.

Each cyclic process is composed of an array of photo bioreactors. Thisarray produces algae cells which serve as fuel to supply the energyneeded to produce the products. The array collects the flue gasesproduced by the combustion of the algae cells and recycles thecombustion products in order to produce the same amount of algae cellsfor an additional cycle of algae cells combustion.

The products of the basic core are:

-   -   1. Cement/quicklime    -   2. Desalinated water    -   3. Ammonia    -   4. An access of algae cells that can be used as a source of        energy (combusted cells as fuel), or for additional various        purposes such as: agricultural products, food additives, etc.        These Four Products can be Produced Only by the Synergistic        Arrangement of the Cycles Described Below.

The Cycles of the Basic Core are:

The Cement/Quicklime Cycle:

The cement production is a heavily polluting CO₂ process and one of themost intensive energy consuming industries. In this system no CO₂ isemitted from the system to the atmosphere and sunlight is the energysource. A certain amount of algae cells are harvested from the photobioreactors, dried and combusted in a kiln in which limestone is firedto produce cement or quicklime. The flue gases with the combustionproducts flow back to the array of the photo bioreactors for recyclingand production of an additional amount of algae cells, which is alsoaimed for combustion in the kiln. The flue gases contain oxidizednitrogen (nitrates and nitrites) that can be used as a source ofnitrogen for the algae cells. The amount of CO₂ in the flue gasesincludes the CO₂ produced by the combustion of the algae cells, and theCO₂ released from limestone during firing. This amount of CO₂ is about3.44 fold higher than the amount of CO₂ that was produced by the algaecells combustion. This additional amount can be used to produce anamount of algae cells which is 3.44 fold higher than the amount of algaecells that is used for limestone firing, but an additional amount ofavailable nitrogen source has to be added to this cycle since the amountof oxidized nitrogen can support the production of the amount of algaecells which at the most is equal to the amount of the cells that arecombusted in the kilns. The required additional amount of nitrogen issupplied by the Ammonia Cycle.

The Ammonia Cycle:

The energy required for ammonia production in the existing plants issupplied by fossil fuels. In this system this energy is supplied bycombustion of dried algae cells. The algae cells for the ammoniaproduction can be allocated from the excess of the algae cells which areproduced by the excess of CO₂ released from the limestone in theCement/Quicklime Cycle.The amount of energy required to produce the amount of ammonia requiredfor the production of the excess of algae cells is only 24% of thecombusted energy content of the excess. Hence, only 24% of the excesshas to be allocated for the ammonia production, and most of the excess(76%) remains for additional purposes. Actually, the amount of algaecells allocated from the excess of the algae cells is supposed to bemuch smaller. The flue gas produced by combustion of the algae cells inthe ammonia plant are not released to the atmosphere but are alsocollected and recycled in the photo bioreactors array. Thus, anadditional cycle of ammonia production is produced, in which an amountof algae cells which is equal to the amount of cells combusted in theammonia plant is produced by the combustion products. By upscale of theammonia plant—an additional amount of ammonia can be supplied for otherpurposes (fertilizers production, etc.).

The Cells Drying/Water Desalination Cycle:

The algae cells, after being harvested, are dried in an array of heatexchangers. The heat energy for cells drying is supplied by the hot fluegases which are produced in the combustion chamber while they flow backto the photo bioreactors. The wet algae cells moving in the oppositedirection are used to cool the flue gases. The energy calculations showthat an additional energy is required to dry the excess of algae cellsproduced by the system. This energy is produced by a separate dryingcycle in which algae cells grown in an array of photo bioreactors areharvested and combusted in a combustion chamber to produce hot fluegases for cell drying. The heat combustion energy in this drying cycleis much higher than the energy required for drying the excess of algaecells and for the drying of the cells produced in the drying cycle. Thecombustion products in the flue gas produced by the drying desalinationcycle is collected and recycled in the photo bioreactors for anadditional cycle of harvesting, drying and combustion of algae cells.Thus, a third cycle is produced—the drying cycle, which provides all oralmost all the energy for the algae cells drying. In this cycle, like inthe other cycles, the source of energy is the sunlight which isconverted to chemical energy by the algae cells.The water which is evaporated from the wet algae cells during the dryingstage is condensed back to liquid water while the flue gases are cooledto the growth temperature before entering the photo bioreactors.Consequently, large amounts of desalinated water are produced in thesystem. Per each gram of quicklime/cement, about 7 grams of desalinatedwater are produced by this system or 7-8 cubic meter are produced pereach ton of cement.The desalinated water can be used for other purposes (agriculture,etc.), while an equivalent amount of sea water is added to the photobioreactors instead the desalinated water.In addition to the cement, ammonia and a huge excess of chemical energy(fuel) and by the same amount of sunlight energy a huge amount ofdesalinated water is also produced by the system.

Recycling of the combustion products: (CO₂ and Oxidized NitrogenCompounds):

The recycling is performed in two stages. At the first stage, thecombustion products are recycled directly by the algae cells from thegaseous phase above the cells suspension in the photo bioreactors towhich the flue gases flow. At the second stage, the flue gases whichleave the photo bioreactors with a very low concentration of combustionproducts react with the ammonia which flows in the opposite direction tothe photo bioreactors as a source of nitrogen. The products of thisreaction (ammonium nitrate, nitrite and ammonium bicarbonate) flow withthe ammonia solution to the photo bioreactors and are also used asnitrogen source.

Additional Cycles:

The excess of cells produced by the basic core can be used as a sourceof combustion energy for other energy requiring plants, such as powerplants, glass industry, etc. The flue gases produced in this plant arenot released to the atmosphere but are also recycled in an additionalarray of photo bioreactors. Thus, a network of integrated cycles ofvarious plants can be established which produces various products. Sincethe recycling of the flue gases released from the combustion chambers ofthe additional plants yields an amount of new algae cells which is equalor close to the amount of the combusted algae cells, such systemsaccumulate energy in the form of algae cells which increasescontinuously. The calculations suggest that the energy can increase intwo ways: arithmetic progression or in geometrical progression,depending on two alternatives of the system arrangement:

-   1. If the rate of limestone firing in the system remains constant,    then the energy accumulates in arithmetic progression.-   2. If all or part of the excess of algae cells is used to increase    the rate of limestone firing, then the energy accumulates in    geometrical progression.    Theoretically this energy accumulation is endless. Practically, at a    certain stage—this process of “energy inflation” has to be stopped    by directing the excess of the algae cells or the excess of CO₂    produced in the system for other purposes. The excess of algae cells    can be used as food, food additives, fertilizers, etc. The excess of    CO₂ can be used for many industrial and commercial such as gazing    drinks, welding devices, etc.

The present invention provides systems and methods for energyproduction. The method comprises the stages: (i) sustaining andregulating an algae culture in an array of at least one photobioreactor, (ii) introducing CO₂ and nitrogen oxides from the combustionchamber of at least one kiln which is arranged for burning limestone anddolomite into clinker, (iii) harvesting algae from the bioreactors, (iv)producing energy in the form of the biomass of harvested algae. Thesystem comprises at least one kiln for burning limestone and dolomiteinto clinker, at least one photo bioreactor for growing algae; pipeworksfor feeding CO₂ and nitrogen oxides from the combustion chamber of akiln to photo bioreactors; and pipeworks for feeding CO₂ released fromburning limestone and dolomite to the array of photo bioreactors, atleast one harvester for taking algae out of the photo bioreactors, anarray of at least one cell dry and means for producing energy in theform of biomass of the algae taken out of the photo bioreactors. In someembodiments of the system, CO₂ from the kiln is used to intensify thegrowth of the algae in the photo bioreactors. A large excess of algae isproduced by this synergetic arrangement, and this access can be used forelectric energy production, water desalination and additional energyconsuming processes.

According to some embodiments, the invention is a synergistic assemblyof concerted closed cyclic processes for production of: energy, fuel,cement/quicklime, desalinated water and ammonia. Some of the devicesproduce energy (fuel) and some of them consume energy and the productsof part of the cycles are the raw materials for other cycles in thesystem. The system comprises of: cement/quicklime production plant,electric energy production plant, water desalination plant, ammoniaproduction plant, several bioreactors and additional energy consumingplants.

-   -   a) The energy supplied to these plants is sunlight energy        converted to chemical combustion energy by algae cells grown in        the photo bio reactors    -   b) The plants of the system are fueled with dried or pyrolized        algae cells produced in the photo bio reactors.    -   c) The CO₂, nitrogen oxides and other waste products produced by        combustion in the system, and the CO₂ released during        clinker/quicklime production, are sequestrated and recycled in        the photo bioreactors for additional cycles of fuel production.        No CO₂ releasing to the atmosphere and no air pollution.    -   d) The system is arranged in such a way that the amounts of        carbon, nitrogen and other precursors for cell growth are        steadily self-increasing by positive feedback. Consequently, the        rate by which the system produces fuel is much higher (about        3.44 fold) than the rate by which the system consumes fuel.        Thus, an excess of sun energy converted to chemical combustion        energy (algae cells) is accumulated in the system by an        accelerated rate.    -   e) In one possible arrangement, when the rate of limestone        firing does not change, excess of energy produced by the system        is accumulated by an arithmetic progression. In a second        possible arrangement, when part of the excess is used to        increase the rate of limestone firing, the excess is accumulated        by geometrical progression. The amount of energy that can be        supplied by this method is theoretically unlimited as long as        there is enough area for algae cell growth.    -   f) The system supplies for itself all the energy required for        its operation. The calculations have taken into account possible        energy leakage in the system and a huge energy excess produced        by this method is the net amount of energy that the system        supply.        The operational energy of the system is supplied by additional        cyclic electric energy production device fueled by algae from        the photo bioreactors array, as was described above (U.S. Pat.        No. 6,477,841 and EP0561436B1).

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention will become more clearlyunderstood in light of the ensuing description of embodiments herein,given by way of example and for purposes of illustrative discussion ofthe present invention only, with reference to the accompanying drawings(Figures, or simply “FIGS.”), wherein:

FIG. 1 is a block diagram illustrating the synergistic integration ofthe three cycles which are the core of the system and the devices whichare geared together to one cyclic system which suppliescement/quicklime, excess of fuel as dried or pyrolized algae cells,desalinated water and ammonia by sunlight energy mediated by algaecells;

FIG. 1 a is the same but without verbal tags, only numbers;

FIG. 2 is a block diagram illustrating a system for quicklime/cement andenergy production, according to some embodiments of the invention.

FIG. 3 is a block diagram illustrating the ammonia production cycle,according to some embodiments of the invention;

FIG. 3 a is a simplified block diagram of the ammonia cycle,illustrating its main outlines;

FIG. 4 is a block diagram of the drying process and water desalination,according to some embodiments of the invention.

FIG. 5 is a block diagram illustrating the stages of the recyclingprocess;

FIG. 6 is a flowchart illustrating a method of producing energy,according to some embodiments of the invention.

FIG. 7 is a flowchart illustrating a method of harvesting algae from thebioreactors according to some embodiments of the invention.

FIG. 8 is a flowchart illustrating optional stages in a stage ofsustaining and regulating an algae culture in photo bioreactorsaccording to some embodiments of the invention.

FIG. 9 is a flowchart illustrating a method of drying and pyrolizingalgae, according to some embodiments of the invention.

FIG. 10 is a flowchart illustrating a method of water desalinationaccording to some embodiments of the invention.

FIG. 11 is a flowchart illustrating a method of CO₂ and nitrogen oxidessequestration according to some embodiments of the invention.

FIG. 12 is a flowchart illustrating a method of cement and quicklimeproduction according to some embodiments of the invention.

FIG. 13 is a flowchart illustrating a method of ammonia productionaccording to some embodiments of the invention.

DETAILED DESCRIPTIONS OF SOME EMBODIMENTS OF THE INVENTION

The present invention includes a system and method for energy productionutilizing CO₂ emitted from burning limestone and dolomite to intensifythe growth of algae in photo bioreactors. The algae biomass is thenutilized to generate energy.

The term “Limestone” as used herein in this application comprisescalcite, dolomite and a combination thereof.

FIG. 1 is a block diagram illustrating the synergistic integration ofall the three cycles and the devices which are geared together to onecyclic system which supplies cement/quicklime, excess of fuel as driedor pyrolized algae cells, ammonia and desalinated water by sunlightenergy mediated by algae cells. Algae cells are grown in an array ofphoto bioreactors 100 supplied with sea water and minerals 120 andsunlight 110. The cells are harvested and the wet algae cells 130 aredried in an array of cells driers 400 which are also heat exchangers tocool hot gases 240 and 320. Part of the dried cells 210 serves as fuelin a kiln 200 for limestone and dolomite 220 firing. Another part of thedried cells 310 serve as fuel for ammonia production plant 300. In thekiln 200 limestone and dolomite 220 are fired to producecement/quicklime 230. The hot flue gases 240 released from the kiln 200are cooled in the array of the cells dryers 400 and so are the hot fluegases 320 which are emitted from the ammonia plant 300. The cold fluegases 410 from the cells dryers array 400 are returned to the array ofphoto bioreactors 100 to recycle the combustion products in the flue gas(CO₂ and NOx compounds) in order to produce additional cycles of algaecells. The amount of CO₂ released from the limestone 220 is about 2.44fold higher than the amount of CO₂ produced by the algae cellscombustion during limestone firing in the kiln 200. Therefore, an excessof CO₂ enters to the photo bioreactors from the limestone firing kilns.Therefore, an additional amount of nitrogen source has to be supplied tothe photo bioreactors in order to recycle the additional amount of CO₂as additional amount of algae cells. This nitrogen is supplied asammonia 330 produced by the ammonia plant 300 fueled by algae cells 310.Remnants of CO₂ and NOx compounds in the used flue gas 140 which leavesthe photo bioreactors array 100 are stripped by interaction with ammoniasolution in a sequestration device 500 to produce ammonium nitrate andammonium, bicarbonate 510 that can be also used as a nitrogen and carbonsource in the photo bioreactors 100. The hot flue gases 240 and 320serve as a source of energy to dry the wet algae cells 130 in the heatexchangers 400. The evaporated water from the cells is condensed whenthe flue gases 410 are cold enough before entering the photo bioreactors100. A significant amount of desalinated water 420 is condensed andaccumulates as desalinated water 420 which is one of the products of thesystem. Simultaneously, a new amount of sea water and minerals 120 aresupplied to the photo bioreactors 100 in the same rate by which thedesalinated water is supplied by the system. A huge amount of sunlightenergy is converted to chemical energy and is accumulated in the systemas dried or pyrolized cells 620 by a positive feedback mechanism and theyield of the system progressively increase. If the rate of limestonefiring is not increased by this excess of energy—the excess of energy isaccumulated in an arithmetic progression. If at least part of thisexcess is used to increase the rate of limestone firing—the energyaccumulates in a geometrical progression. At a certain stage thisincreasing of the yield of the system 600 has to be stopped, and theexcess of the energy has to be directed to other usages 630 by attachingto the system other energy requiring plants such as electric powerplant, glass plants, metallurgical plants, etc. Part of the excess canbe supplied as wet cells 610 for other usages 630 such as foodadditives, animals feeding, etc.

The Cement/Quicklime Cycle:

The rise in the concentration of CO₂ in the atmosphere indicates thatthe rate with which the biosphere assimilated CO₂ as biological carboncompounds is slower than the rate with which CO₂ is released by fuelconsumption. This low productivity of the biosphere is the result of thelow CO₂ concentration in the atmosphere and an adaptation of theexisting ecological system to this low concentration.

One way to meet the requirements for carbon compounds is to establish anew artificial ecological system with higher productivity. Thisecological system may be based on fast growing photosynthetic organismsand high concentration of CO₂ that can support higher growth rate. Thereis only one source of enough CO₂ for this purpose and that is calcite(CaCO₃) and dolomite (MgCO₃).

Almost all of the CO₂ on the surface of the world had been deposited aslimestone and dolomite. The carbon in the limestone is not utilizable bythe cells due to the low solubility of limestone and the negative freeenergy of the reaction between calcium and bicarbonate ions. Limestoneis an endless resource of carbon for useful energy production.Fortunately the energy required to release the CO₂ from limestone is nottoo high, and the direction of the process can be reversed by thesunlight energy captured by the photosynthetic cells. The by product andby benefit of this process is quicklime and cement, which are producedby sunlight energy (mediated by cells without any cost for energy, andare highly required products anyhow).

According to some embodiments of the invention, the process is cyclic,continuous, closed to the carbon and nitrogen sources of the system(CO₂) and nitrogen source (ammonia and nitrogen oxides) with highproduct yield and a very high yield of light energy converted tochemical energy. Some of the advantages of the system are:

-   -   1. Cement and quicklime production has been one of the most        energy intensive industries in the world (about 40-50% of the        production cost). In this system the energy is supplied by the        sun.    -   2. Cement and quicklime production are very heavy air polluting        industries by CO₂—About 9% of the total CO₂ emitted yearly to        the atmosphere. In this system all or almost all of this CO₂ is        sequestrated and used to grow continuously additional cycles of        micro algae cells.

Additional advantages of the cement cycle system are:

-   -   The materials are recycled (CO₂, sea water and nitrogenous        compounds);    -   Cheap equipment and materials;    -   Cheap operation cost;    -   High yield of algae and therefore higher product yield;    -   Self supplying energy and nutrients;    -   Mass production.

According to some embodiments of the invention, most of the heat energyreleased during cell burning is produced by 2 reactions: Oxidation ofhydrogen atoms to water, in which ΔH°=121 KJ/mol Hydrogen atoms. 100 gof cells contain by mass about 8 g of hydrogen (8%). By burning 100 g ofcells the heat energy released by hydrogen oxidation is about 121 KJ/ghydrogen·8 g=968 KJ, or about 9.68 KJ/g hydrogen. The energy (ΔH°f)released during carbon oxidation to CO₂ is about 394 KJ/mol. The atomicmass of carbon is 12 g/mol. By dividing the molar energy released byburning of carbon by its atomic mass, the value of the heat energyreleased by burning 1 g of carbon is 32.8 KJ/g. About 50% of the cellmass is carbon. When burning 100 g of cells, the heat energy releasedfrom carbon oxidation is 50 g Carbon·32.8 KJ/g=1642 KJ, or about 16.42KJ/g cells. Hydrogen and carbon contribute about 55-60% of the driedcell mass, and by burning them the heat energy produced is about(16.42+9.68) KJ/g cells=26.1 KJ/g cells. Taking into account oxidationof other elements contained in the cell—the heat energy produced isabout 25 KJ/g cells. Algae cells are thus comparable to anthracite coalwith 23 KJ/g. According to various reports, the combustion energy ofalgae cells varies in the range of 18-30 KJ/gram/cells. Therefore, forthe following calculation below, it is assumed that the combustionenergy of the cells is 25 KJ/gram/cells.

According to some embodiments of the invention, the system and methodutilize cheap and non-polluting quicklime and cement (CaO) production.The proposed invention includes energy production by sunlight energywith micro-algae cells. Calcium oxide is usually made by the thermaldecomposition of materials such as limestone, that contain calciumbicarbonate (CaCO₃); mineral, name calcite, according to the equationCaCO₃+Heat→CO₂+CaO. When the temperature is between 800-1200 DegreesCelsius, the product is quicklime known also as burnt lime. At 1400Celsius Degrees the product is clinker. The main operational cost ofquicklime and cement production is the energy (about 40-50%). The rawmaterial of cement production (Lime Stone) is very cheap, only a fewpercents of the overall operational costs. The kiln is fueled with drymicro algae cells.

According to some embodiments of the invention, the proposed system iscyclic and closed for the carbon source. All CO₂ released by burning themicro algae cells and during calcium oxide production is collected andflowed into the photo bioreactors to enable additional cycles of cellgrowth. Limestone (calcite and dolomite) is an excellent source of CO₂for photosynthesis. During CaO production a huge amount of CO₂ isreleased from the limestone. 1 mol of CaCO₃ decompose to 1 mol of CaO(M=56 g/mol) and 1 mol of CO₂ (M=44 g/mol). Each ton of limestonedecomposes to about half ton of quicklime and about half tone of CO₂.

According to some embodiments of the invention, and according to variousreferences, the energy required to produce 1 ton CaO or 1 ton cement isabout 4,000-4,600 MJ, or the energy required to produce 1 gram of CaO isabout 4.6 KJ/g. The molecular mass of CaO is (40+16) g/mol=56 g/mol. Theenergy required to produce 1 mol of CaO is: 4.6 KJ/g CaO·56 g/mol=257.6KJ/mol CaO. Since by burning 1 gram of cells, the amount of heat energyproduced is about 26 KJ/g cell, then in order to produce 1 mol of CaOthe amount of cells that have to be burned is 257.6 KJ/26 KJ/g cells=9.9g cells. Assuming that the carbon content of the cells is 50% (4.93 gcarbon), by burning 9.9 g cells, the amount of CO₂ released is:4.93 g carbon/12 g carbon/mol=0.41 mol CO₂.

The amount of CO₂ emitted from the limestone is much higher than theamount of CO₂ that was produced by burning cells to release this CO₂from the limestone. Approximately 2.44 fold: 1 mol CO₂ fromlimestone/0.41 mol CO₂ from cells=2.44.

By supplying this amount of CO₂ (released from limestone) to additionalphoto bioreactors combined with the system, an additional amount of newcells is produced. This amount of the new cells is greater then theamount of the cells that have been burnt to release the CO₂ from thelimestone by a factor of 2.44 fold. Taking into account that the CO₂ inthe flue gas is completely (or almost completely) recycled, the amountof the new cells is higher by a factor of about 3.44 fold compared tothe original amount of burnt cells. At the next stage, the amount of CaOand new cells also increases by a factor of 3.44 and so on.

FIG. 2 is a block diagram illustrating a system for quicklime/cement andenergy production, according to some embodiments of the invention. Thesystem comprises at least one kiln 200 for burning limestone anddolomite 220 into cement/quicklime 230. Kiln 200 is heated with energy(dried or pyrolized algae cells as fuel 210) and burning limestone anddolomite 220 produces large amounts of CO₂ 231. The system furthercomprises at least one photo bioreactor 100 for growing algae,comprising a container 102 with water and algae and a regulation unit104. Photo bioreactors 100 receive sea water and minerals 120 andsunlight 110. The photo bioreactors 100 also receive CO₂ 231 releasedfrom the limestone and CO₂ and NOx compounds 240+410 which are containedin the flue gases produced in the combustion chamber of the kilns 200during algae combustion and these are regulated by regulation unit 104.

Additional nitrogen source is ammonia 330 which is produced in theammonia plant 300 of this system and additional nitrogen compounds 510which are produced in the stripping device 500 (not shown in thisfigure). This nitrogen sources enable the production of the excess ofalgae cells 600 produced by the excess of CO₂ 231 released from thekilns 200.

The system is closed and cyclic. The gases and the liquid materials inthe system flow through a net of pipe works connecting the variousdevices of the system as well as further possible attached plans. TheCO₂ 231 released from the limestone 220 as well as the ammonia 330 andthe nitrogen compounds 510 intensify the growth of the algae in photobioreactors 100, while the CO₂ and NOx compounds produced by algaecombustion enable the production of algae cells in the same rate bywhich they are combusted for limestone firing. The system furthercomprises a harvester 135 for taking algae suspensions 125 out of photobioreactors 100 by pumps 131. The algae are harvested by filters 132 andthe wet algae cells 130 are conveyed for drying in the heat exchangers400. The water remained after the filtration 121 is fed back to thephoto bioreactors 100.

FIG. 12 is a flowchart illustrating a method of cement and quicklimeproduction according to some embodiments of the invention. The methodcomprises the stages:

-   -   Providing limestone to at least one firing kiln (stage 4001);    -   Providing dried or pyrolized algae to fuel the kilns from the        heat exchangers/cell driers (stage 4002);    -   Firing limestone by combusted algae cells (stage 4003).    -   Providing hot flue gases from the kilns to the heat        exchangers/cell driers (stage 4004).    -   Collect cement and quicklime (stage 4005).

A large excess of algae is produced by this synergetic arrangement.

According to some embodiments of the invention, substantially all CO₂released by burning limestone and dolomite into clinker in kiln 200 isintroduced into photo bioreactors 100. According to some embodiments ofthe invention, at least one analyzer may be connected to a controlsystem, and arranged to keep the CO₂ and nitrogenous compounds (nitrogensources) concentration in photo bioreactors 100 at an optimal level(e.g. 0.1% concentration of CO₂ in the gaseous phase of the photobioreactors 100). The control system 104 also regulates the harvestingof the algae cells to the appropriate rate according to theirconsumption in the various plants of the system. The algae concentrationin the cells suspensions 102 are held fixed and the rate of harvestingis equal to their growth rate.

There are two possible kinetics by which the algae cells excess isincreasing (the inflation process) with various combinations and variousproportions between them:

-   a. CO₂ amplification. All or part of the new excess cells is used to    release an additional amount of CO₂ by increasing the amount of    limestone firing. The result is a successive cascade of    amplifications. With this arrangement, the energy produced by the    system is accumulated by a geometrical progression. If all of the    excess is used to increase the rate of CaO production, the capacity    of the system progresses geometrically with a factor of about 3.44.    Even if only a part of the excess cells is used to increasing the    amount of limestone firing, the capacity of the system still    progresses geometrically with a factor smaller then 3.44 as long as    the process is cyclic and the amount of CO₂ that remains in the    system at a certain stage is greater than the amount of the previous    one. This means that the amount of sunlight energy that is converted    and accumulated by the cells as chemical energy is also increasing    geometrically.-   b. The rate of CaO production does not increase. All of the excess    new cells (that are produced with the CO₂ released from limestone)    are not used to increase CaO production. Taking into account that    CO₂ in the flue gases of the additional consuming plants included in    the system are also sequestrated, the amount of cells which    accumulate in the system increases by an arithmetic progression with    an increment of 2.44 g of new cells per every 1 g of cells consumed    in the kilns.

Theoretically, this increasing process is endless and the amount ofenergy that the system can supply is unlimited. The only practicallimitation is available areas on the globe. Obviously, at a certainstage this increasing process should be stopped by using the excess ofproduced new cells or the excess of CO₂ for additional applications.

There are two alternative usages to this increasing excess of biomassand energy:

-   a. Enlargement of the system by adding more and more energy    consuming plants such as electric power plant, glass industries,    etc. Practically, this enlargement must be stopped at a certain    size.-   b. Use of at least part of the new cells produced by the system, and    at least part of the CO₂ released from limestone for other utilities    such as:    -   1) The excess of CO₂ can be supplied to additional Photo        bioreactors in which other kind of micro algae cells (or other        photosynthetic organisms) grow and produce other important        products (food, Omega 3, Vitamin C, source of protein, food        additives, animal feeding etc).    -   2) Bio-diesel production.    -   3) Chemical industries like ammonium bicarbonate, liquid and        solid CO₂ production, rubber and plastics industry,        pharmaceuticals and petroleum industry, silicone production        etc.).    -   4) Hydrogen (H₂) production (by electrolysis).

The Ammonia Cycle:

The nitrogen oxides produced during algae cells combustion can beup-taken by algae cells and recycled in the closed cyclic systems, butthe amount of these nitrogen oxides enables the production of no morethen 1 gram of new cells per each gram of consumed cells. Production of3.44 grams of new cells per each gram of consumed cells requiresadditional amounts of nitrogen for production of the rest 2.44 grams ofnew cells. These additional amounts are supplied as ammonia (NH₃).

Cells contain about 14-15% Nitrogen by mass. Ammonia is produced byHaber-Bosch process at high temperature (400-500° c.) and high pressure(300-1000 at). Although the reaction between nitrogen and hydrogen isvery exothermic (ΔHf°=−94 KJ/mol Ammonia) the activation energy is veryhigh, and this is one of the most intensive energy consuming industrialprocesses. According to various references, the specific energyconsumption of ammonia production varies between 40 KJ/g ammonia to 28KJ/g ammonia. Taking an average value of 35 KJ/g ammonia, the energyconsumed for production of 1 mol ammonia is about:35 KJ/g ammonia·17 g/mol ammonia=595 KJ/mol ammonia.100 g cells contain about 1 mol of Nitrogen (14-15% by mass, M=14 g/molnitrogen).Since Every Mol of Nitrogen in the Cells is Supplied by a Mol ofAmmonia,595×)/mol ammonia is the energy required to produce the ammonia forgrowth of 100 g cell. For production of 1 g cells the required amount ofenergy is: 5.95 m/g cells which is only 24% of the combustion energy ofthe cells (25-26 KJ/g cell). Hence, in order to produce 2.44 grams ofnew cells, 12% of this amount, which is 0.59 gram cells has to becombusted in the ammonia production plant.

FIG. 3 is a block diagram illustrating the ammonia production cycle. Theammonia production plant 300 is fueled by dried or pyrolized algae cells310. The hot flue gas 320 produced in the ammonia plant is cooled in acell drier-heat exchanger 400, and is used as source of CO₂ and nitrogenoxides for production of similar amount of new wet cells 130 in a photobioreactors 100. These new cells are harvested 135, dried in the celldrier 400, and combusted in the ammonia production plant 300, as asource of energy. The ammonia 330 flows into the sequestration device500 in opposite direction to the used flue gas 140 that leaves the photobioreactors 100. Remnants of CO₂ and NOx compounds in the used flue gas140 which leaves the photo bioreactors array are stripped by interactionwith ammonia solution 330 in a sequestration device 500 to produceammonium nitrate and ammonium bicarbonate. This mixture 510 serves as anitrogen and carbon source in the photo bioreactors.

The input energy of 5.95 KJ/g cells for ammonia production is requiredfor the photo bioreactors in which the excess of cells is produced (bythe CO₂ emitted from limestone). Theoretically, if the fuel for ammoniaproduction is supplied as algae cells, about 24% of the excess has to beallocated for ammonia production. Actually, this amount can be muchsmaller. The ammonia production plant 300 within such system is fueledby dried or pyrolized algae cells 310 and the flue gas 320 produced inthe ammonia production plant 300 is recycled and used as source of CO₂and nitrogen oxides for production of similar amount of new cells in thephoto bioreactors array 100 connected to the plant. Thus, an additionalammonia production cycle can be created in which new cells are dried andcombusted in the ammonia production plant as a source of energy. All, oralmost all, of the cells used for ammonia production can be new cellsproduced by this cycle and only a small amount (if any) has to beallocated from the excess.

FIG. 13 is a flowchart illustrating a method of ammonia productionaccording to some embodiments of the invention. The method comprises thestages:

-   -   Providing dried or pyrolized algae to fuel the ammonia        production from the heat exchangers/cell driers (stage 5001);    -   Supplying atmospheric nitrogen (N2) and hydrogen source (stage        5002);    -   Producing high pressure and temperature by combustion of the        dried or pyrolized algae (stage 5003).    -   Ammonia production (stage 5004).    -   Providing aqueous ammonia solution from the ammonia production        plant to the stripping device and to the photo bioreactors        (stage 5005).    -   Providing hot flue gases from the ammonia plant to the heat        exchangers/cell driers (stage 5006).

Drying and Pyrolysis of Algae Cells and Water Desalination:

the specific evaporation energy of water (ΔHev) at 25° C. is 2.4 KJ/gwater. More than 90% of the harvested cell's content is water, and wateralso exists among the cells. Hence, the specific evaporation energy ofthe cells is approximately similar to that of water, i.e. 2.4 KJ/gcells. Loss of heat energy to the surrounding has also been kept in mind(a loss of about 30% with good isolation), thus the actual evaporationenergy of 3.1 Kj/g cells is a reasonable approximation. This amount ofenergy is about 12% of the heat energy content of the cells. Inexperiments with closed cycles it has been demonstrated that the heatenergy in the flue gases is enough, or almost enough, to dry theharvested cells burnt in the cycle (for electric energy production,etc.). But in these experiments the amount of the dried new recycledcells was equal to the amount of the burnt cells. In the proposed systemthe amount of new cells is not equal but higher by 3.44 folds, comparedto the original amount of burned cells for quicklime firing. Therefore,it is doubtful whether the energy in the flue gas produced duringquicklime firing is enough for drying all the amount of the new producedcells.

FIG. 4 is a block diagram of the drying process and water desalination.Let's assume that the amount of heat energy required to dry the excessof algae cells is produced by burning a part of cells which are takenfrom the excess of the dried cells 620. This part 440 is taken from theheat exchangers—cells driers array 400 and combusted in a combustionchamber 430 which adds appropriate amount of hot flue gas 450 to theheat exchangers-cells driers array 400. Theoretically, this part issupposed to be 12% of the excess 620, but actually this part is expectedto be much smaller (if any). The combustion products in the flue gas 450produced by these burnt cells 440 are added to the flue gases 410 thatflow to the photo bioreactor array 100 and are also recycled in thephoto bioreactors array 100 which supplies cells to the drying devices400 as is described by FIG. 4. The result is a closed drying cycle inwhich the energy for the drying process is sun energy 110, mediated byphotosynthetic cells and most, or almost most, of the cells burnt inthis cycle are produced by the cycle itself and are not taken from theexcess. As can be seen from the above calculation, the system has enoughenergy to dry the cells it produces and still a substantial proportionof energy is left for additional purposes.

The conditions in the drying process (lack of oxygen, 500° c.) can beadjusted in such a way that all or part of the cells is pyrolized duringdrying. The system can produce a liquid fuel of pyrolized cells inaddition to whole intact dried cells. This liquid fuel can be used by:

a. Additional devices which are not included in the system

b. Devices which are included in the system when liquid fuel istechnologically preferred.

The flue gas 410 that leaves the cell driers array 400 contains a lot ofwater. This water is produced in the combustion chambers 430, in thelimestone kiln 200, in the ammonia plant 300 and during evaporation fromthe wet cells 130 in the drying device 400. In order to flow the fluegases 240, 450 and 320 into the photo bioreactors 100 their temperaturehas to be lowered in the heat exchangers of the drying device 400 to thegrowth temperature of the algae cells 410. At this temperature, thewater is condensed back again to the liquid state. This wateraccumulates in the heat exchanger 400 and in the storage of cold fluecontainer 415. This is desalinated water 420 that may contain very smallamounts of NOx compounds which are harmful to human beings and animalsbut can serve as a nitrogen source for plants. This water 420 can bereturned to the photo bioreactors 100 together with the other combustionproducts, but a better option is to use it as desalinated water forother purposes, while same amount of sea water are added to thephoto-bioreactors instead of the desalinated water. The NOx compoundscan be absorbed by filters in order to use this water by human being andanimals or to irrigate plants.

FIG. 9 is a flowchart illustrating a method of drying and pyrolizingalgae, according to some embodiments of the invention. The methodcomprises the stages:

-   -   Providing hot flue gases from kilns and combustion chambers to        at least one heat exchanger (stage 1001);    -   Providing wet harvested algae cells to at least one heat        exchanger (stage 1002);    -   Drying or pyrolizing the cell algae by the hot flue gases (stage        1003); and    -   Fueling the kilns and the combustion chambers by the dried or        the pyrolized algae (stage 1004).    -   Supplying partially cooled flue gases saturated by water vapor        for water desalination (stage 1005).

FIG. 10 is a flowchart illustrating a method of water desalinationaccording to some embodiments of the invention. The method comprises thestages:

-   -   Providing partially cooled hot flue gases saturated by water        vapor from the heat exchangers/cell driers to at least one        storage/cooling tank (stage 2001);    -   Vapor condensation (stage 2002);    -   Supplying cooled flue gases to the photo bioreactors (stage        2003); and    -   Collecting desalinated water from the bottom of the        storage/cooling tank (stage 2004).

In large industrial scales, such systems can be a significant source offresh water. More then 90% of the wet cell content is water, and thereis also water among the cells. Hence, approximately 0.95 gram ofdesalinated water can be obtained from 1 gram of wet algae cells andapproximately 9.5 gram of desalinated water can be obtained from 1 gramof dried algae cells. From each gram of dried cells which are aimed forlimestone firing—3.44 gram of new dried cells are produced. Therefore,about 32 grams of desalinated water are produced by each cycle of thelimestone firing process. An additional amount is added from the ammoniaproduction cycle. Per each 3.44 grams of dried cells in the limestonecycle, 0.59 grams of dried cells are combusted in the ammonia cycle.Hence the ammonia cycle contributes about 5.6 grams of desalinated waterper each cycle of the limestone firing process. To the amounts ofdesalinated water produced in the limestone cycle and the ammonia cycle,additional amounts are added from the drying cycle itself and from thecombustion chambers in where the hydrogen in the dried cells is oxidizedto water. Since per each gram of dried algae cells combusted forlimestone firing about 5 grams of cement are produced, it can beconcluded that per each gram of cement, about 7-8 grams of desalinatedwater are produced in addition to the surplus of cells excess and by thesame amount of sunlight energy.

CO₂ and NOx Sequestration:

According to some embodiments of the invention, the method comprisesrecycling of the CO₂ and NOx compounds in the flue gas according to thefollowing material balance calculation. FIG. 5 is a block diagramillustrating the stages of the recycling process. The concentration ofCO₂ in the exhaust gas of engines or power plant varies between 3% whenthe fuel contains high hydrogen content (hydrocarbon) and 15% when thefuel is coal (close to 100% carbon). Since cells contain about 50%carbon, it is assumed that the cold exhaust gas of burnt cell 410 whichenters to the gaseous phase 105 above the cells suspensions 102 containsan average value of 8-9% of CO₂. Hence, most of the volume of theexhaust gases is not CO₂ but other gasses. Since most of the volume ofthe flue gas is not CO₂ or NOx compounds, and the space in the photobioreactor is limited, most of the exhaust gas must be released from thephoto bioreactor with part of the CO₂ and NOx compounds in the exhaustgas, and cannot be completely recycled by the micro algae in the growthmedium 102. The concentration of the CO₂ in the gaseous phase 105 iskept by controlled supply rate 900 of cold flue gas with 8-9% CO₂concentration 410 from the flue gas containers 415, flow into the photobioreactors 105. CO₂ sensors 930 continuously feed the control systemwith data 920 and the concentration of the CO₂ in the gaseous phase 105is kept at about 0.1% by open/shut signals 910 from the control system.These open/shut signals regulate the valves which control: (1) The flowof the cold flue gas 410 into the photo bioreactors 105; (2) The flow ofthe used flue gas 140 from the gaseous phase of the photo bioreactors105 to the stripping device 500; (3) The flow of the stripped flue gas141 from the gaseous phase 501 of the stripping device to theatmosphere. This implies that the rate by which the CO₂ is supplied tothe cells suspensions 102 by the cold flue gas 410 is equal to the rateby which the algae cells in the suspension assimilates the CO₂ from thegaseous phase 105. CO₂ concentration of about 0.1% is about 3 foldhigher then the CO₂ concentration in the atmosphere. In suchconcentration, the growth rate of the algae cells is maximal or closedto the maximum. While cold flue gas 410 with 7-8% CO₂ concentrationflows into the photo bioreactor, equal flow (same volume) of used fluegas 140 leaves the bio reactor, with CO₂ concentration of about 0.1%.This implies that most of the CO₂ in the flue gas (about 98.7%) issequestrated directly by the growing cells. Similar proportions of theNOx compounds are also sequestrated directly by the cells.

The remained 0.1% CO₂ and the NOx compounds that leave the photobioreactors with the used flue gas 140 are stripped in the strippingdevice 500. In this device, the gaseous phase 501 is in contact with theammonia solution 331 that flows from the ammonia production plant 300 inopposite direction. The CO₂ in the used flue gas reacts with the ammonia(NH₃) to produce ammonium bicarbonate (NH₄CO₃). The nitrate ions reactwith the ammonia to produce ammonium nitrate (NH₄NO₃) Experiments showthat more than 90% of the CO₂ react with the ammonia. Thus, the strippedflue gas 141 that is released to the atmosphere from the ammonia tankcontains only about 0.01-0.02% CO₂, much less then the CO₂ concentrationin the air (about 0.033%). The mixture of ammonia, ammonium nitrate andammonium bicarbonate 510 is than supplied to the cells suspension 102 asa nitrogen source. Sensors 940 feed the control system with data aboutthe ammonia concentration in the cells suspension 950 and the flow ofthe nitrogen to the cells suspension is controlled by open/shut signals960 that control the flow of this mixture 510 to the cells suspension102.

FIG. 11 is a flowchart illustrating a method of CO₂ and nitrogen oxidessequestration according to some embodiments of the invention. The methodcomprises the stages:

-   -   Providing cooled flue gases containing about 7-8% CO₂ from the        storage/cooling tank to the photo bio reactors (stage 3001);    -   Assimilation of dissolved CO₂ and nitrogen oxides by algae cells        (stage 3002);    -   Providing sequestrated flue gases with residual CO₂ and nitrogen        oxides (about 0.1% CO₂) from the photo bio reactors to the        stripping device (stage 3003).    -   Providing aqueous ammonia solution from the ammonia production        plant to the stripping device (stage 3004).    -   Reacting of the residual CO₂ and nitrogen oxides with the        aqueous ammonia solution (stage 3005).    -   Providing the mixture of the aqueous ammonia solution and the        reaction products from the stripping device to the photo bio        reactors as an available source of nitrogen and carbon (stage        3006).    -   Releasing stripped flue gases (about 0.01% CO₂) from the        stripping device to the atmosphere (stage 3007).

FIG. 6 is a flowchart illustrating a method of producing energy,according to some embodiments of the invention. The method comprises thestages:

-   -   Sustaining and regulating an algae culture in one or more photo        bioreactors (stage 90);    -   Introducing cooled CO₂ and nitrogen oxides from at least one        storage/cooling vessel for water desalination (stage 91);    -   Harvesting algae from the bioreactors (stage 92); and    -   Producing energy from the biomass of harvested algae (stage 93).

FIG. 7 is a flowchart illustrating a method of harvesting algae from thebioreactors (stage 92), according to some embodiments of the invention.The method comprises the stages:

-   -   Pumping water out of photo bioreactor (stage 800);    -   Filtering the water to extract algae from it (stage 810);    -   Drying extracted algae (stage 820); and    -   Burning said dried extracted algae (stage 830).

According to some embodiments of the invention, the method furthercomprises feeding at least part of CO₂ and heat resulting from burningdried extracted algae (stage 830) back into at least one of the photobioreactors (stage 840).

According to some embodiments of the invention, the method furthercomprises feeding at least part of the water extracted during filtrationof the extracted algae (stage 820) back into at least one of said photobioreactors (stage 850). A control mechanism regulates the algae celldensity and the rate of cell harvesting to be equal to the algae growthrate.

FIG. 8 is a flowchart illustrating optional stages in a stage ofsustaining and regulating an algae culture in photo bioreactors (stage90), according to some embodiments of the invention. The stage ofsustaining and regulating an algae culture in photo bioreactors (stage90) may comprise any of the following stages or a combination of thesestages:

-   -   Installing a sheet at the bottom of the photo bioreactor (stage        700);    -   Installing a partly reflecting sheet at the top of the photo        bioreactor (stage 710);    -   Installing a covering sheet above the photo bioreactor (stage        720);    -   Utilizing heat exchange with the external sources (stage 730);        and    -   Fine tuning of the temperature with heating elements and cooling        elements connected to the photo bioreactor (stage 740).

The above calculations indicate that energy problems of the globe arenot quantitative as long as the sun rises and enough area is availableto absorb sunlight by the photosynthetic cells. The current inventionsuggests some solutions for both aspects of these energy problems. Whenoil is extracted from cells (about 50% of the cell dry weight) and istrans-esterified, too much energy is consumed for the production of thefuel (biodiesel), and too large part of the energy content of the cellis not extracted and lost. Consequently, no net energy (or only smallamount of energy) is left. Therefore it is preferred to fuel kilns (forCO₂ production and other processes) with cells instead of fossil fuel.Most of the air is nitrogen, more than 79%, so there is no lack of thisresource. On the other hand, the concentration of CO₂ in the air is only0.03%, too low to enable “bioenergy” production in appropriate rate. Ifit is wished to reduce consumption of fossil fuels, or to save them forother utilities such as row materials for petro chemical industries,another source of CO₂, except fossil fuel, must be found. Almost all ofthe CO₂ on the surface of world had been deposited as limestone. Thecarbon in the limestone is not utilizable by the cells due to the lowsolubility of limestone and the negative free energy of the reactionbetween calcium and bicarbonate ions. Limestone is an endless resourceof carbon for useful energy production. Fortunately the energy requiredto release the CO₂ from limestone is not too high, and the direction ofthe process can be reversed by the sunlight energy captured by thephotosynthetic cells. The by product and by benefit of this process isquicklime, cement and desalinated water, which are produced by sunlightenergy (mediated by cells) without any energy cost.

Even if cyclic systems with photosynthetic cells as discussed above arevery efficient for sunlight energy transmission per each mass unit, theoverall capacity of such systems may be too small, not because of lackof energy. The sunlight energy is supplied in huge excess, and only atiny part of this energy can be used by us. The limiting factor isenough amount of material to transfer it. The amount and theconcentration of CO₂ in the air are too small to do it with the requiredamount and rate. The amount of carbon in the atmosphere (in the form ofCO₂) is estimated as 750 billions ton of carbon. The annual amount ofcarbon released to the atmosphere by fossil fuel combustion is about 5.5billions ton of carbon, and this amount is increasing geometrically eachyear. If the fossil fuel has to be replaced by fuel which is produced byphotosynthetic cells, we have to supply those photosynthetic cells withcarbon (CO₂) in a similar rate of 5.5 billions tons of carbon per year.If this amount has to be supplied by the atmosphere, it is relatively asignificant part of its carbon content: 5.5/750=1/136.4=0.73% of theoverall carbon in the air. Taking into account that the CO₂ is dispersedall over the atmosphere, only a very small amount of this CO₂ isavailable to photosynthesis and the annual supply by the atmosphere istoo small. According to various reports, the global amount of CO₂ whichis absorbed by the oceans and the biosphere per year is about half ofthe annual amount of CO₂ which is released to the atmosphere.Consequently, the rate and the amount of CO₂ that the atmosphere cansupply are much lower then what is needed for fuel production byphotosynthetic cells. For that reason, the sunlight energy stored by thephotosynthetic cells is transferred to an endless source of utilizablecarbon (limestone) in order to amplify the amount of CO₂ needed toenhance the capacity of the system. A cyclic process amplified by CO₂ isnot only an efficient way to supply energy; it is apparently the onlypossible way to supply energy in appropriate quantities and rate byphotosynthetic cells in a large (global) scale. Let's assume that wehave produced by sun energy an amount of fuel on a large scale, burnedit, and the waste product has been dispersed to the environment. Whereanother similar amount of CO₂ can come from? The amount andconcentration of CO₂ in the atmosphere is too small. There is an endlesssource of CO₂ (limestone), but we need energy to use it. For the timebeing, this CO₂ is released by fossil fuel, but this is exactly what weare trying to prevent. The only way to get out of this “Catch CO₂” is bykeeping the waste products within the system for reuse, combined withCO₂ amplification by limestone firing.

According to some embodiments of the invention, the quantity of CO₂released from burning algae and limestone may allow growing 3.44 timesthe algae burnt. The system actually produces desalinated water andclinker from limestone utilizing solar energy in the mediation of algae.The system accumulated biofuel in the form of algae to an amountexceeding manifolds the consumed amount of fuel. The source of carbon isCO₂ from limestone and the source of energy is the sun. The energysurplus may be consumed to produce electricity etc. The system does notemit CO₂ but recycles carbon and nitrogen sources. The system mayincrease its energy production geometrically, as long as area andlimestone are available. The system is simple and requires cheapmaterials, yet produces unlimited amounts of energy, thus reducing fuelprices.

In the above description, an embodiment is an example or implementationof the inventions. The various appearances of “one embodiment,” “anembodiment” or “some embodiments” do not necessarily all refer to thesame embodiments.

Although various features of the invention may be described in thecontext of a single embodiment, the features may also be providedseparately or in any suitable combination. Conversely, although theinvention may be described herein in the context of separate embodimentsfor clarity, the invention may also be implemented in a singleembodiment.

Reference in the specification to “some embodiments”, “an embodiment”,“one embodiment” or “other embodiments” means that a particular feature,structure, or characteristic described in connection with theembodiments is included in at least some embodiments, but notnecessarily all embodiments, of the inventions.

It is understood that the phraseology and terminology employed herein isnot to be construed as limiting and are for descriptive purpose only.

The principles and uses of the teachings of the present invention may bebetter understood with reference to the accompanying description,figures and examples.

It is to be understood that the details set forth herein do not construea limitation to an application of the invention.

Furthermore, it is to be understood that the invention can be carriedout or practiced in various ways and that the invention can beimplemented in embodiments other than the ones outlined in thedescription above.

It is to be understood that where the claims or specification refer to“a” or “an” element, such reference is not be construed that there isonly one of that element.

It is to be understood that where the specification states that acomponent, feature, structure, or characteristic “may”, “might”, “can”or “could” be included, that particular component, feature, structure,or characteristic is not required to be included.

Where applicable, although state diagrams, flow diagrams or both may beused to describe embodiments, the invention is not limited to thosediagrams or to the corresponding descriptions. For example, flow neednot move through each illustrated box or state, or in exactly the sameorder as illustrated and described.

Methods of the present invention may be implemented by performing orcompleting manually, automatically, or a combination thereof, selectedsteps or tasks.

The term “method” may refer to manners, means, techniques and proceduresfor accomplishing a given task including, but not limited to, thosemanners, means, techniques and procedures either known to, or readilydeveloped from known manners, means, techniques and procedures bypractitioners of the art to which the invention belongs.

The descriptions, examples, methods and materials presented in theclaims and the specification are not to be construed as limiting butrather as illustrative only.

Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined.

The present invention can be implemented in the testing or practice withmethods and materials equivalent or similar to those described herein.

While the invention has been described with respect to a limited numberof embodiments, these should not be construed as limitations on thescope of the invention, but rather as exemplifications of some of thepreferred embodiments. Those skilled in the art will envision otherpossible variations, modifications, and applications that are alsowithin the scope of the invention. Accordingly, the scope of theinvention should not be limited by what has thus far been described, butby the appended claims and their legal equivalents.

What is claimed is:
 1. A system comprising: an array of photobioreactors arranged to produce wet algae; an array of cell dryersarranged to receive said wet algae produced by the array of photobioreactors and dry the wet algae to produce dry or pyrolyzed algae fromthe produced wet algae, and flue gas; at least one kiln arranged toproduce cement or quicklime from limestone or dolomite, the at least onekiln capable of being heated by burning said dry or pyroglazed algaeproduced by the array of cell dryers, and is arranged to supply hot fluegas to the cell dryers; an ammonia production plant heated by burningsaid dry or pyrolyzed algae produced by the array of cell dryers, andfurther arranged to supply hot flue gas to the cell dryers; adesalination module arranged to condense desalinated water from the fluegas obtained from the cell dryers, after being cooled in a specifiedvessel; and a stripping device arranged to: receive ammonia from theammonia production plant which flows in one direction and flue gas whichflows from the photo bioreactors in an opposite direction; enable achemical reaction between the ammonia and residual nitrogen oxides andCO2 contained within the flue gas to yield nutrients; and supply thephoto bioreactors with the nutrients and the ammonia, wherein the arrayof photo bioreactors, the at least one kiln, the ammonia productionplant, and the stripping device operate in a closed cyclic process thatyields accumulated amounts of algae.
 2. A method comprising: producingwet algae within an array of photo bioreactors; drying said produced wetalgae in an array of cell dryers to produce dry or pyrolyzed algae fromthe produced wet algae, and flue gas; producing cement or quicklime fromlimestone or dolomite in at least one kiln being heated by burning saiddry or pyrolyzed algae; supplying hot flue gas from the at least onekiln to the cell dryers; heating an ammonia production plant by burningsaid dry or pyrolyzed algae, to yield a supply of hot flue gas to thecell dryers; condensing desalinated water from the flue gas obtainedfrom the cell dryers by cooling the hot flue gas in a specified vesselin operative association with a desalination module; receiving ammoniafrom the ammonia production plant which flows in one direction and fluegas which flows from the cell dryers in an opposite direction; enablinga chemical reaction between the ammonia and residual nitrogen oxides andCO2 contained within the flue gas from the cell dryers to producenutrients; and supplying the photo bioreactors with said producednutrients and the ammonia, wherein the array of photo bioreactors, theat least one kiln, the ammonia production plant, and the strippingdevice operate in a closed cyclic process that yields accumulatedamounts of algae.